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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Frank van der Linden , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260331113724.2080833-1-songmuchun@bytedance.com> <81857888-b6aa-4f04-bfd7-e9365d62669d@linux.ibm.com> <1ACF04AC-CC9B-4B29-8E3F-6609B5C1B09E@linux.dev> Content-Language: en-US From: Donet Tom In-Reply-To: <1ACF04AC-CC9B-4B29-8E3F-6609B5C1B09E@linux.dev> X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: GdFtizFs75ZFdD075faTNMxTinhIm0gu X-Authority-Analysis: v=2.4 cv=frzRpV4f c=1 sm=1 tr=0 ts=69ce0fe3 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=r77TgQKjGQsHNAKrUKIA:9 a=VnNF1IyMAAAA:8 a=968KyxNXAAAA:8 a=NZoFHl13bqaJ-IwmEIUA:9 a=QEXdDO2ut3YA:10 a=ZRGaOfixQ7KW42RQcCAA:9 a=WTK3bPQC7c9GO7MO:21 a=_W_S_7VecoQA:10 a=lqcHg5cX4UMA:10 X-Proofpoint-ORIG-GUID: ghaV165Dd5E7jhx6j-um4nuUH6KENxmh X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDAyMDA1NCBTYWx0ZWRfX0miuM9m/DlUo cjDhPq1TRyCLXKK/1Hf0lfGiu2It5SeRKk0DfgjQPjdNWAoXxnn+okxS3CCP5bIg/jDT+vcxaNG ejvIETdkWXDRYd1Mij0HTadUPx/XJ2eKwie/mwxgLEBRHM/AC54SKvFiwCR2z7Dhm2HVpZsz5eM L1b1nEOuERKcY8J12C4pM4qf8Calcx5944G3ZfHkYIXLhBn09cpc3YpYuKco1gFqjIWfik/k8K5 Zpts0k5b8B28lEuUaqvne2zAdlEFnQmgLCnwkart2UBDD5rhTZn6BUYh3i6VbIOTMc6nQ+Friqy wF+DoHAetw7FJ87KBFHmhWbG+xitTdNqjhnPpn4M5gmT1FUih38LzolTonb3wkByZr97uphBIAF qpvod6+iAgwK8UP3oXpC+8ZYs2448qMOSPq257gMTfL9j8lfJMqGf0r8ixqVeZJEa82swQjesFW khu5e02lVUdEaLzTCPQ== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-02_01,2026-04-01_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 spamscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 lowpriorityscore=0 bulkscore=0 adultscore=0 suspectscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2604020054 X-Rspam-User: X-Stat-Signature: 4jrfy1zf6zpneohxaupfusjbyef7d4wh X-Rspamd-Queue-Id: 7820EC0009 X-Rspamd-Server: rspam09 X-HE-Tag: 1775112176-391758 X-HE-Meta: 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 X7Rv7X+V 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This is a multi-part message in MIME format. --------------LspP04RDqWezW5Pn7kgxlFRK Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/1/26 7:58 AM, Muchun Song wrote: > >> On Apr 1, 2026, at 02:34, Donet Tom wrote: >> >> Hi Muchun > Hi, > >> On 3/31/26 5:07 PM, Muchun Song wrote: >>> sparse_init_nid() is careful to leave alone every section whose vmemmap >>> has already been set up by sparse_vmemmap_init_nid_early(); it only >>> clears section_mem_map for the rest: >>> >>> if (!preinited_vmemmap_section(ms)) >>> ms->section_mem_map = 0; >>> >>> A leftover line after that conditional block >>> >>> ms->section_mem_map = 0; >>> >>> was supposed to be deleted but was missed in the failure path, causing the >>> field to be overwritten for all sections when memory allocation fails, >>> effectively destroying the pre-initialization check. >>> >>> Drop the stray assignment so that preinited sections retain their >>> already valid state. >>> >>> Fixes: d65917c42373 ("mm/sparse: allow for alternate vmemmap section init at boot") >>> Signed-off-by: Muchun Song >>> --- >>> mm/sparse.c | 1 - >>> 1 file changed, 1 deletion(-) >>> >>> diff --git a/mm/sparse.c b/mm/sparse.c >>> index c2eb36bfb86d..3a14b733bf71 100644 >>> --- a/mm/sparse.c >>> +++ b/mm/sparse.c >>> @@ -584,7 +584,6 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin, >>> ms = __nr_to_section(pnum); >>> if (!preinited_vmemmap_section(ms)) >>> ms->section_mem_map = 0; >>> - ms->section_mem_map = 0; >> >> This looks correct to me. >> >> I have a couple of questions: >> >> 1. As I understand, section_mem_map initially stores the nid >> during early boot, and later it stores a pointer to an >> array of struct page. In sparse_init_nid(), the struct page >> array is stored in section_mem_map via >> sparse_init_early_section(). If >> __populate_section_memmap() fails, we are clearing the nid >> stored in section_mem_map right? > Right. > >> 2. Another question: if sparse_init_nid() fails for some >> sections, there is no retry mechanism to add them again, >> correct? > Right. > >> 3. when ms->section_mem_map is set to 0 >> for a pre-initialized section, does it only affect the >> pre-initialization check, or could it lead to other issues? >> > Only affect pre-initialization. No other issues. Thanks for the clarification. This looks good to me. Reviewed by: Donet Tom > > Thanks. > >> - Donet >> >>> } >>> } > --------------LspP04RDqWezW5Pn7kgxlFRK Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit


On 4/1/26 7:58 AM, Muchun Song wrote:


On Apr 1, 2026, at 02:34, Donet Tom <donettom@linux.ibm.com> wrote:

Hi Muchun

Hi,


On 3/31/26 5:07 PM, Muchun Song wrote:

sparse_init_nid() is careful to leave alone every section whose vmemmap
has already been set up by sparse_vmemmap_init_nid_early(); it only
clears section_mem_map for the rest:

        if (!preinited_vmemmap_section(ms))
                ms->section_mem_map = 0;

A leftover line after that conditional block

        ms->section_mem_map = 0;

was supposed to be deleted but was missed in the failure path, causing the
field to be overwritten for all sections when memory allocation fails,
effectively destroying the pre-initialization check.

Drop the stray assignment so that preinited sections retain their
already valid state.

Fixes: d65917c42373 ("mm/sparse: allow for alternate vmemmap section init at boot")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/sparse.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index c2eb36bfb86d..3a14b733bf71 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -584,7 +584,6 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
  ms = __nr_to_section(pnum);
  if (!preinited_vmemmap_section(ms))
  ms->section_mem_map = 0;
- ms->section_mem_map = 0;


This looks correct to me.

I have a couple of questions:

1. As I understand, section_mem_map initially stores the nid
   during early boot, and later it stores a pointer to an
   array of struct page. In sparse_init_nid(), the struct page
   array is stored in section_mem_map via
   sparse_init_early_section(). If
   __populate_section_memmap() fails, we are  clearing the nid
   stored in section_mem_map right?

Right.


2. Another question: if sparse_init_nid() fails for some
   sections, there is no retry mechanism to add them again,
   correct?

Right.


3. when ms->section_mem_map is set to 0
   for a pre-initialized section, does it only affect the
   pre-initialization check, or could it lead to other issues?


Only affect pre-initialization. No other issues.


Thanks for the clarification.

This looks good to me.

Reviewed by: Donet Tom <donettom@linux.ibm.com>




Thanks.


- Donet


  }
 }
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